By way of background, a physician or other healthcare professional (collectively, “physician”) often uses wire guides in a variety of medical procedures. For instance, the physician commonly uses wire guides as one preferred instrument for the placement of another elongate medical device, such as a catheter or stent delivery system, into a vessel passageway. The term “passageway” includes any lumen, chamber, channel, opening, bore, orifice, flow passage, duct, or cavity for the conveyance, regulation, flow, or movement of bodily fluids and/or gases of an animal. As examples of the various passageways into which wire guides may be utilized, physicians frequently use wire guides in medical procedures that involve placing a wire guide in the passageways of an aorta, artery, bile duct, blood vessel, brachial, bronchiole, capillary, esophagus, fallopian tube, gall bladder, gastrointestinal tract, heart, intestine, liver, pancreas, stomach, trachea, ureter, urethra, vein, and other locations in a body (collectively, “vessel”) to name a few. Similarly, physicians may place wire guides through a working channel of an endoscope (or an accessory channel used with an endoscope) in endoscopic medical procedures such as those described below.
As a backdrop to an understanding of a conventional endoscope, these medical instruments generally include a light source and image sensor for visualizing the interior of an internal region of a body. In the field of endoscopy, physicians use a variety of different endoscopes in a wide range of applications. These different types of endoscopes include, by way of example, the following: arthroscope, bronchoscope, choledochoscope, colonoscope, cytoscope, duodenoscope, gastroscope, laparascope, neproscope, sigmoidoscope, utererscope, or any external accessory channel device used with any of the foregoing (collectively, “endoscope”).
In exemplary endoscopic uses of wire guides, a physician introduces at least a portion of the wire guide through a working channel of an endoscope or an accessory channel external to an endoscope. As another alternative, the physician inserts at least a portion of the wire guide through a catheter lumen, which catheter the physician has already inserted, or intends to insert, into the endoscope working channel or accessory channel.
In exemplary percutaneous uses of wire guides, a physician inserts the wire guide into the vessel passageway by a variety of suitable methods. In one instance, the physician may create an incision in a region of the patient's body, position a cannula at the incision, and then insert the wire guide through the cannula. Alternatively, the physician may insert a needle—containing the wire guide—into a vessel such as an artery, bile duct, brachial vein, cephalic vein, pancreatic ducts, or other vessel as described above, and then introduce the wire guide through the needle into the vessel passageway. In a subsequent step, the needle is withdrawn over the wire guide.
In these various wire guide uses, physicians and others normally evaluate and select wire guides with respect to several performance criteria including: column strength, flexibility, and torsional stiffness. As one criterion, the column strength of a wire guide must be sufficient to allow the wire guide to be pushed through the endoscope or accessory channel, the catheter, or the patient's vessel passageway without kinking or prolapsing. In another criterion, the flexibility of a wire guide must be sufficient to navigate a tortuous vessel passageway and to avoid damaging the vessel through which the physician advances the wire guide. A third performance criterion of a wire guide relates to its torque-ability or steerability. This third criterion denotes the extent to which a wire guide possesses the capability of transferring a torque in a one-to-one relationship from the proximal end to the distal end of the wire guide without excess twisting that may result in a whipping effect caused by torque build-up in the wire guide.
Depending upon the materials used to construct the wire guide, the above three characteristics are often interconnected or interrelated to one extent or another. In other words, often with some wire guides these performance criteria compete in that an increase in one criterion compromises another criterion. For example, increased column strength may mean a decrease in flexibility, and vice versa. Indeed, when constructing wire guides, the limits of the metals used for making conventional wire guides often necessitate sacrificing one performance characteristic in favor of another. By way of example only, increasing the torque-ability of a given wire guide may often decrease the flexibility and/or pushability in a wire guide of conventional composition or shape.
In order to negotiate a tortuous path of a vessel passageway or to avoid passageway obstacles during insertion as described above, conventional wire guides have a proximal end that is sometimes held by or otherwise secured by a physician, and a distal end to be located at or near the target site. As is conventional, “distal” means away from the physician or operator when the device is inserted into a patient, while “proximal” means closest to or toward the physician or operator when the device is inserted into a patient.
The shape of a typical wire guide is normally generally cylindrical with a substantially circular cross section to mimic the configuration of the vessel passageway or the channel of an endoscope or accessory device. Some conventional wire guides occasionally have stainless steel or nitinol wire cores wrapped in a longitudinal Teflon coated coil, thereby increasing the diameter and stiffness of the wire guide and making the wire guides hydrophobic and resistant to coating with a hydrophilic material and/or therapeutic agent. By comparison, conventional non-coiled wire guides typically have a smooth outer surface and a tapered distal end with a reduced diameter measured in thousandths of an inch diameter, thereby increasing the flexibility of the wire guide but decreasing the outer surface area at the distal end of the wire guide. Improvements are possible to achieve flexibility while also increasing surface area to provide a wire guide with more functionality.
Therefore, improved wire guides would be desirable. As taught herein, these wire guides comprise novel approaches to tailoring wire guides to have increased outer surface areas and/or reservoirs for enhancing hydrophilic properties and for delivering therapeutic agents.